The present invention relates to an exhaust gas muffler for internal combustion engines, especially for two-stoke engines of manually guided implements, such as power chain saws, brush cutters or the like. The muffler has a housing that includes at least two shells, wherein one of the shells is provided with at least one outlet opening for the exhaust gas, and whereby a cover is disposed over the at least one outlet opening for guiding the exhaust gas, with at least one discharge opening being provided in the cover for the discharge of the exhaust gas to the surrounding air.
WO 96/25590 discloses an exhaust gas muffler for an internal combustion engine in a portable implement. The exhaust gas muffler essentially comprises two shells that form a housing, with a partition extending between the shells. The partition divides the housing into two chambers, with the exhaust gas flowing out of the internal combustion engine into one of the chambers. Thereafter, the exhaust gas passes into the second chamber within the other shell, and from there the exhaust gas is guided through a tube to an outlet opening that is again disposed in the first shell. By means of this position of the outlet opening, the exhaust gas that exits the exhaust gas muffler is supposed to be mixed as intensively as possible with the cooling air stream of the internal combustion engine that is directed toward the exhaust gas muffler. This results not only in a rapid cooling of the exhaust gas stream, but also a cooling of the exhaust gas muffler, thereby reducing the temperature of the outer surfaces of the muffler. No measures are provided for preventing the discharge of sparks.
DE 25 39 516 A1 discloses an exhaust gas muffler for internal combustion engines for commercial agricultural and forestry implements. Since during operation of the implement the exhaust gas muffler gets very hot, this publication proposes that the wall of the exhaust gas muffler that contains the outlet opening be covered by a dish-shaped wall, with a cooling channel having a nozzle-like narrowed portioned being formed between the wall of the muffler and the covering wall. Adjoining this narrowed portion is a diffuser-like widened portion into which pass the exhaust gases that flow out of the outlet opening, whereupon they are mixed with the cooling air drawn in by the injector effect of the nozzle-like narrowed portion. Again with this arrangement, no measures are taken to prevent the discharge of glowing particles.
U.S. Pat. No. 4,370,855 describes an exhaust gas muffler for internal combustion engines in a manually guided implement, whereby a cover is secured to the outer side, i.e. the side remote from the internal combustion engine; the cover forms cooling channels between itself and the exhaust gas muffler. Disposed within the housing is a diffuser element that is surrounded by a screen that is intended to restrain particles carried along in the exhaust gas stream. The exhaust gas stream exits on that side of the exhaust gas muffler adjacent to the internal combustion engine, whereby the exhaust gas stream, via appropriate deflection, is supplied to the outer side of the exhaust gas muffler. In order to prevent the exhaust gas muffler from being overheated, it is necessary to direct the cooling air stream of the internal combustion engine against the exhaust gas muffler so that this cooling air stream reduces the temperature of the outer side of the muffler housing. With this known arrangement, the screen element must be made of high temperature resistant material since it is disposed in the immediate vicinity of the inlet opening through which the exhaust gases enter the exhaust gas muffler. Thus, the wires that form the screen cannot be as thin as would be desired, so that the mesh width of the screen element is also correspondingly large.
It is an object of the present invention to provide an exhaust gas muffler of the aforementioned general type whereby the discharge of particles along with the exhaust gas stream is significantly reduced.